The invention described herein was made in the course of, or under a contract with the National Science Foundation.
Synthesis of a series of compounds including ternary lead molybdenum sulfides was reported in "Sur de Nouvelles Phases Sulfurees Ternaires du Molybdene" by Chevrel et al., Journal of Solid State Chemistry 3, 515-519 (1971).
Subsequently it was reported by Matthias et al. in Science 175, 1465 (1972 that several of these compounds were superconducting. In particular the compound having the composition Mo.sub.5.1 Pb.sub.0.9 S.sub.6 was described as having a superconducting transition temperature Tc of 13.2-12.5 K. Neither Chevrel et al. nor Matthias et al. described in detail how the compounds were prepared.
Further work on these compounds was reported by other researchers in the field. Marezio et al. in "Superconductivity of Ternary Sulfides and the Structure of PbMo.sub.6 S.sub.8 ", Mat. Res. Bull., Vol. 8, pp 657-668 (1973) apparently erroneously attributed to Matthias et al. in their publication the finding of Tc = 15.2 K for the lead molysulfide identified in the title. The paper does not describe in detail how the compounds were prepared except they were apparently made in stages, for example, preparing the lead sulfide first.
Odermatt et al. in a "Letter to the Editor", J. Phys. C: Solid State Physics, Vol. 7, 1974, L13-14, showed in a graph, FIG. 1, Pb.sub.0.9 Mo.sub.5.1 S.sub.6 having an extropolated H.sub.c2 of 450 kG. Preparation of the compound involved direct reaction of the constituents in evacuated quartz tubes at 1050.degree. C for 24 hours followed by pressing and annealing.
Fischer et al. in a "Letter to the Editor", J. Phys. C: Solid State Phys., Vol. 7, 1974, L450-453, describes similar compounds, speculating that 600 kG can be obtained at 4.2K. These workers do not describe in detail how the compounds were made.